<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .top {
      display: flex;
      width: 872px;
      height: 32px;
    }
    .Column {
      width: 289px;
      text-align: center;
      color: #999999;
    }
    .events {
      width: 289px;
      text-align: center;
      color: #999999;
    }
    .role {
      width: 289px;
      text-align: center;
      color: #999999;
    }
    .active {
      color: black ;
      border-bottom: 3px solid orange;
      background-color: azure;
    }
    .video-list {
      display: flex:block;
    }
  </style>
</head>
<body>
  <div class="top">
    <div class="Column">
      精品栏目
    </div>
    <div class="events">
      赛事精品
    </div>
    <div class="role">
      英雄攻略
    </div>
    <script>
      var topEl = document.querySelector(".top")
      var currentActive = null
      topEl.onmouseover = function(event)
      {
        if(currentActive) currentActive.classList.remove("active") 
        event.target.classList.add("active")
        currentActive = event.target
      }
    </script>
     
  </div>
</body>
</html>